Geo-replicated storage with scalable deferred update replication

Many current online services are deployed over geographically distributed sites (i.e., datacenters). Such distributed services call for geo-replicated storage, that is, storage distributed and replicated among many sites. Geographical distribution and replication can improve locality and availability of a service. Locality is achieved by moving data closer to the users. High availability is attained by replicating data in multiple servers and sites. This paper considers a class of scalable replicated storage systems based on deferred update replication with transactional properties. The paper discusses different ways to deploy scalable deferred update replication in geographically distributed systems, considers the implications of these deployments on user-perceived latency, and proposes solutions. Our results are substantiated by a series of microbenchmarks and a social network application.